The present invention relates to a charging and distribution device for shaft furnaces, particularly blast furnaces. More particularly, this invention relates to a charging and distribution device which comprises a rotary distribution spout adjustable in its angle of inclination and installed inside the throat of a furnace, particularly a high capacity blast furnace operated at high pressures.
Recent developments in the field of high capacity blast furnaces have resulted in increasingly exacting demands on the charging devices employed in such furnaces. One important concept adopted for the purpose of improving the efficiency of such blast furnaces is to try to insure that the throat gas will pass through the furnace charge in the optimum manner. If this object is to be realized in present day blast furnace designs, which attempt to achieve increasing size and higher operating pressures, even distribution of the charging material in the blast furnace is required. Since the configuration with which the charge or burden is distributed over the surface of the hearth of the blast furnace depends directly on the charging device employed, it can easily be understood that the charging device may contribute considerably to the improvement in the efficiency and operation of a blast furnace if it enables the charging operation to be controlled exactly as desired.
Two basic types of charging devices are presently known in the art. The first, which has been in use for many years, employs two superimposed bells of unequal diameter. These bells have to be extremely large if they are to be suitable for and fit large diameter blast furnaces. The size of these bells must increase proportionally with the increase in size of blast furnaces. Such bells represent a substantial investment cost, and they present serious difficulties when they have to be repaired or replaced. Furthermore, when employing such bells it is not possible to introduce the charge in an even and uniform manner over the surface of the blast furnace. As is well known in the art, a hollow is unavoidably formed underneath the lower bell, thus resulting in a characteristic M curve configuration of the charge surface. Thus, the important object of achieving a uniform distribution of the charge or burden cannot be realized when the two bell charging configuration is employed.
The second category of charging devices, which is achieving increased acceptance and use, is a bell-less charging apparatus which operates on the principle of a rotatable and angularly adjustable spout. The spout is rotatable and adjustable to distribute the charge inside the furnace to permit the charging configuration or profile to be controlled as desired. This bell-less charging installation is described in U.S. Pat. No. 3,693,812, and improvements are disclosed in U.S. Pat. Nos. 3,814,403 and 3,880,302. The three above-identified U.S. patents are all assigned to the assignee of the present invention, and reference is hereby made thereto for details of the features disclosed in those patents.
The basic concept of the rotatable and angularly adjustable spout charging device incorporates a pair of storage tanks for holding the charging material, the storage tanks being alternately emptied via an intake chute into a rotatable distribution spout installed in the throat of the blast furnace. The spout is mounted so as to be rotatable about the axis of the blast furnace and angularly adjustable with respect to the axis of the blast furnace so that it can be tilted. The charge configuration can be modified or controlled by varying the rate of rotation and/or the angle of inclination of the charging spout.
The mechanisms which rotate the spout and adjust the angle of inclination of the spout in the above mentioned patents all require two separate control devices to effect rotation and angular displacement of the spout, and they have their control devices partly exposed to furnace throat gas. While these systems have proven to be useful and successful, it is, nonetheless, desired to effect an additional improvement to the rotatable and adjustable charging chute concept as set forth in this invention.